Electric lamp with unitary inner envelope and stem assembly and manufacture thereof



July 13, 1965 s. K. DANKO 3, ,6 ELECTRIC LAMP WITH UNITARY INNER ENVELOPE AND STEM ASSEMBLY AND MANUFACTURE THEREOF Filed June 18, 1962 neg Geo

United States Patent ELECTRIC LAMP WITH UNITARY INNER EN- This invention relates to electric lamps and to methods of manufacturethereofa v I It is a principal object of the invention to provide a novel lamp structure incorporatinga light source enclosed in a compact inner envelope or chamber which is'enclosed in a larger outerbulb or envelope. It is a further object to provide such a structure capable of assembly and manufacture on high-speed, automatic equipment, and therefore adaptable to production in high volume at relatively low cost. It is a still further object to provide a structure of the type described adaptable for use in conventional sockets and fixtures for general lighting purposes.

seal to define a sealed inner chamber between the said In recent years there has been introduced on the market an incandescent filament lamp having a high efficiency for a long useful life with virtual freedom .from blackening, all made possible by operating a tungsten filament in a compact bulb containing, in addition to the usual gas filling, a quantity of halogen which serves as a regenerative getter. During operation of the lamp, the walls of the compact bulb are heated to a uniformly high temperature, and tungsten vapors normally volatilized from the filament at its high operating temperature and deposited on the bulb walls, combine chemically with the halogen to form a tungsten-halogen compound which migrates to the vicinity of the hot filament where it is dissociated to release tungsten which redeposits on the filament, the halogen returning to the bulb walls to combine with further quantities of tungsten deposited thereon, thereby repeating the cycle. Particularly good results have been obtained in lamps employing iodine as the re generative getter as disclosed and claimed in Patent 2,883,571, Fridrich'et al., which is assigned to the same assignee as the present application.

In order to achieve and maintain proper operating conditions, including temperature and spacing between bulb wall and filament, for effectivefunctioning of the tungsten-halogen cycle, the enclosing envelope or bulb must be of compact size. It has also been the practice to make such lamps in a double-ended construction wherein the lead-in conductors extend into opposite ends of the small tubular envelope with the filament extending axially through the length of the envelope. Such a. structure requires special bases or terminals and is evidently not adaptable for use in the sockets and fixtures for general purpose lamps which comprise a relatively large bulb having a neck portion to which is attached a base, conventionally a screw-threaded base. It is therefore a particular object to make available the advantages of high efiiciency and long life ofthe tungsten-halogen principle in a lamp having the physical or structural characteristics of a general lighting lamp.

In'accordance with one aspect of the invention, the abovestated objects are achieved in a structure wherein the lamp comprises an outer glass bulb or envelope having a neck portion and which may be of a size and shape such as those employed in general service lighting lamps for' ordinary household or commercial or industrial applications. A re-entra'nt inner envelope extends into the interior of the outer bulb and has a closed inner end and an open-outer'end sealed to the neck portion of the outer bulb. The said inner envelope has, intermediate its inner and-outer ends, a seal portion whereat the walls of the envelope are collapsed or compressed to form a hermetic seal portion and the closed inner end of the inner envelope. The light source, preferably a tungsten filament, is located within the said inner chamber and is electrically connected at its ends to respective lead-in conductors which have portions thereof hermetically sealed in said seal portion and which extend outwardly through the open outer end of said inner envelope.

In accordance with a further aspect of the invention, the assembly of inner envelope, filament and lead-in wires is consolidated into a unit, or inner assembly, prior to insertion of that assembly into the outer bulb. Also in accordance with a preferred aspect of the invention, that assembly further includes a glass exhaust tube which extends into the interior of the inner envelope through its open end. During formation of the said seal portion of the inner envelope, the softened walls of the inner envelope are preferably compressed around the inner end of the exhaust tube and sealed thereto without closing off the passage through the interior of the exhaust tube. The said inner chamber portion of the inner envelope is then evacuated and filled with the desired atmosphere through the said exhaust tube. The said inner chamber is then closed otf preferably by reheating a localized portion of the walls of the seal portion and collapsing or compressing those walls to seal off the opening in the exhaust tube. Another localized portion of a wall of the seal portion may then be pierced to forman exhaust aperture communicating with the interior of the exhaust tube to enable subsequent exhausting and gas filling of the outer bulb.

The lamps may then be completed by attachment of a conventional base to the neck portion of the outer bulb and attachment of the lead-in conductors to the base contactsor terminals. 7

Further features and advantages of the invention will appear from the following detailed description taken in conjunction with the drawing, wherein:

FIG. 1 is an elevation, partly in section, of a lamp'embodying the invention;

FIGS. ,2 to 10 illustrate various steps in the assembly and fabrication of the lamp; and

FIG. 11 is an elevation, in section, showing an intermediate stage in the manufacture of the lamp in accordance with a modified procedure;

Referring to FIG. 1 of the drawing, the lamp illustrated therein comprises an outer glass bulb 1 having a neck portion 2 and which may be evacuated or filled with a suitable gas such asnitrogen. The bulb 1 contains an internal assembly including a re-entrant inner glass envelope 3 having a closed inner (upper) end 4 and an open outer (lower) end 5 which is flared outwardly and is sealed by fusion at 6 to the neck 2 of the outer bulb. The inner envelope 3 has, intermediate its ends, a seal portion 7 whereat the walls of the envelope 3 are fused and collapsed or compressed to form a hermetic seal thereby constituting the upper portion of the envelope 3 a hermetically sealed chamber 8. The chamber portion 8 of inner envelope 3 contains a filament 9, preferably a coiled or coiled-coil tungsten filament extending axially of the chamber 3. The filament 9 is connected at its ends to respective longer and shorter lead-in wires 10 and 11 which have portions thereof hermetically sealed in the seal por- The filament 9 may be additionally supported by a supv plemental support wire 16 (see FIG. .5) which has one end embedded in abutton portion 17 at the upper end of the exhaust tube 12 and its other'end formedinto a loop encircling the filament 9 at its midpoint.

The bulb 1 has attached thereto a base '18 which may be a conventional screw thread base comprising a screwthreaded sheet metal shell 19'cemented to the bulb neck. The lead wires and 11 are connected,"respectively,to an end or center .contact'20 andto the shell 19.

The inner chamber 8 containing the tungsten filament 9 preferably constitutes a compact high intensity "incandescent lamp-of the type operating with a halogen regenerative cycle, preferably a tungsten-iodine cycle as.described and claimed in the aforesaid Patent 2,883,571.

To that end, the chamber 8 contains an inert gas filling such as nitrogen, argon, krypton or xenon or mixtures thereof at a pressure'of preferably at least several hundred millimeters of mercury or even exceeding atmospheric pressure. Additionally, the chamber 8 contains a small quantity of iodine which, during operation of the lamp, maintains the walls of the chamber free from deposits of tungsten 'vaporized from the filament9. In view of the requisite relatively high operating temperature, wherein the walls of the chamber 8 attain a temperature in-excess of 250 C., for example approximately 500 C., the en velope 3 is made of glass having a relatively high softening point, such as-one of thewell known so-called hard glasses like borosilicate or alumino-silicate glasses, or quartz glass. The outer bulb 1 is preferably made-of a compatible glass. The lead wires10 and 11 are preferably of tungsten which forms a hermetic seal with such glasses which have a lowcoeflieient of expansion. However, when desired, the outer portions of the lead wires 10 and 11 located below and outside the seal area 7 may be made of other metal such as copper or nickel.

It will be evident that the outer bulb I may be of a size and shapelike that-of conventional household lamp bulbs,

and it may be provided with a frosted or-ditl'using coating or a metallic reflecting coating. The filament 9 may be of any desired capacity such as, for example, about I50 watts or more for operation from conventional power supply sources of about 110 or 220 volts. Thereby, as compared to conventional household lamps operating at, for example, about 16 lumens per-watt for 750 hours in the popular 100 watt size, lamps of the halogen cycle type may be operated atefiieiencies of, for example, 20 to lumens per watt for a life in excess of 2000 hours and with virtually no depreciation in light output during life.

In accordance with a further aspect of the invention, the assembly and manufacture of the lamp may be carried out substantially as follows. In the tfirst step, illustrated in FIG. 2, the upper end of the exhaust tube 12 is heated and upset to form the button 17., and one end ofa straight length of support wire 16, preferably of tungsten, is inserted into the softened button 17. During this operation the exhaust tube 12 may be supported in a support member or spindle 21 as shown somewhat diagrammatically in FIG. 3, the said holder 21 being one of a number of such holders carried at the periphery of the indexing turret of a mount making machine similar to those well known in the art. The exhaust tube is loaded into an axial passage 22 in the holder 21 with its bottom engaging a shoulder 23, the passage being sealed by an O-ring seal 24.

Straight lengths of'the lead wires 10 and 11 are dropped into respective passages 25 and 26 in the holder2l and come to rest on a shoulder 27. Then the upper'cnds of the lead wires 10 and II are Iormcdto provide laterally bent portions 28 withzhooksin-the ends.thereof into which are inserted the :ends'of the'xfilamer'tt '9, after which the hooks are clamped .toifirmly grasp *the'fila'ment.

In the next step, the--supportwire 16 is bent to the shape shown-in FIG. Savith a 'loop inits free .end encir cling the filamentu9 at'its-midpoint.

:from oxidatiomafter whichazone ofthe envelope 3 adja cent the .upper end ofthe exhaust f'tllbZIZ is heated by flames from'burners'indicated at 131. 'TheburnersS Lare actually directed at the tenvelope-3 .in directions at right .angles to those shown in FIG.:.6, that;is, -the.y..are located at opposite sides of the plane containing the lead wires 10 and 111. The said zone is heated toils softening point I and .the walls of the envelope-'3, are eo'llapsedtan'd then compressed by a pairtofypinch jaws (not shown) -'to form a seal area'7 .'(FIGS."7 and'8) in whichare hermetically sealedand embedded portions o'f'thelead -wires 1'0tand 11. The .said' pinch jaws are relieved ormotched atthecenter in :known manner so that the 'i'nnenwalls :o'f envelope .3 in area 7. are fused .and hermetically sealed 10 the outer .walls of the :exhausttube 12 withoutclosing'the passage throughtheinteriorof the exhaust tube.

If desired, the portions of lead wires -10.and' 1-1:wliich are embedded .in the seal 17 may be gprecoated :or beaded 'with glass in known manner.

The *assemblyfthus' formed and showniin '7, is then removed from the :holder .21 #(FIG. 3) and transferred to-exhaust and gas .filling equip'ment *in 'which fit is preferably supported in an inverted position .HStShOWIIidIl FIG. 9. The chamberportion 28 of the tassembly-tis vthen exhausted and filled with. the desired tgas fillirvgQsuh as argon anda-small quantity of'iodine. During the steps of filling with gasand with iodine vapor, the lower end of the chamber 8 is preferably cooled -with liquid nitrogen to .dondense the :iodine vapor. "Then the chamber :8 is sealed off as shown atjl-3 in FIGS, apreferablyby locally heating the walls of the seal area 7 with .burners indicate'd at 32 and either permittingthe glass to "collapse-or compressing-withzpinch jaws to form the seal 13.

Next, .an aperture :14 (FIG."9) is formed :ina'wall of the seal area 7 at a pointspaced 'from-the seal 13and in communication with the interior. of the exhaust tube .12.

The aperture 14 is prefer-ably vformed 'by localized heating and softening-of the glass' with a burner 33 andapplication of compressed air to the-,inter'ior ot-the exhaust tube 12 to blowout the aperture 14.

In the next step, the assembly shown in FIG. 9 .may be transferred to a conventional.sea'ling in machine where an outer glass bulb 1 (FIG. 10):is vdropped over-the .internal assemblvof envelope 3vand associatedelements, and the *neckpottion'Z-of the bulb is fused tandhermetically sealed .to the flared end 5 ot the envelope =3 :to form the. seal 6.

The interior of the outer btilb 1 as then evacuated through the exhaust tube .12 :by way of aperture 14,. and is preferably filled with :a :desired :gas, such .at nitrogen at about 600 mm. I-Ig pressure. The exhaust fibe -:12 is then tipped otf as shown at 15 (FIG. 1.)..a'fter 'w-hic'h-ithe base 21 8 is mounted on the bulb i-neek' and the lead wires 10 and '11 connected thereto in conventional manner.

In FIG. 11 there is illustrated .a zmodification'iin :the manu'thcture-of the internal assembly. -In this case the closed upper end 4 of the envelope .3 i8 iprov'ided with a glass exhaust tabulation .34.- Also. during formation of the seal portion7'. it is compressed in :a manner *tot'clnse or seal olT the exhaust tube 1.2, ra-fter w hich it is reheated and the :exhaust aperture 14' is -l)lown through the mass of plastic glass. The chamber 8 is then evacuated and filled with the desired atmosphere through the tubulation 34 which is then sealed or tipped off as illustrated by the dotted lines at 35. The said inner assembly is then sealed into an outer bulb l as described in connection with FIG.

10, the said outer bulb being exhausted and gas filled and the other end open, with a glass exhaust tube ex tending into the interior of said envelope through the open end thereof, and with a pair of lead-in conductors extending longitudinally into the interior of said envelope beyond said exhaust tube and supporting thereat a filament connected at its ends to the ends of said conductors, heating and softening a, zone of said envelope located intermediate its ends and adjacent to the inner end of said exhaust tube, compressing the softened walls of the envelope at said vzone to form a single hermetic pinch seal area about the adjacent portions of said conductors and about said exhaust tube while preserving the opening through the interior of said tube to thereby form a chamber enclosing said filament between the closed end of said envelope and the said hermetic seal area, removing the air from said chamber through said exhaust tube and filling the chamber with a desired atmosphere, reheating a portion of said hermetic seal area adjacent said chamber to soften and collapse the glass thereat to seal oilthe opening through said exhaust tube, forming an exhaust aperture through the wall of another portion of said seal area incommunication with the interior of said exhaust tube, inserting the resulting assembly into the interior of an outer glass bulb through an open neck portion of the bulb, sealing together the peripheries of said bulb neck portion and the outer end of said envelope, evacuating said outer bulb through said exhaust tube and exhaust aperture, and then sealing off said exhaust tube.

References Cited by the Examiner UNITED STATES PATENTS DAVID J. GALVIN, Primary Examiner.

JAMES D. KALLAM, Examiner. 

